1. Field of the Invention
The present invention relates to a rotary electric machine for use in, for example, for an electric vehicle (EV) or for a hybrid electric vehicle (HEV) and, more particularly, relates to the retaining structure of a bearing.
2. Description of the Related Art
As a conventional rotary electric machine for use in for an electric vehicle (EV) or for a hybrid electric vehicle (HEV), in the case where the carrier frequency of an inverter is set to be high in the case of operating the inverter, voltage (axis voltage) generated in a shaft of an alternating-current motor on the basis of high-frequency induction increases, a potential difference present between an inner ring and an outer ring of a bearing that supports a shaft increases, and an electric current flows in the bearing.
A problem exists in that the current flowing in the bearing causes corrosion referred to as electrolytic corrosion on both inner ring and outer ring tracks and on the rolling surfaces of rolling elements, and accordingly durability of a rolling bearing deteriorates.
Furthermore, a preload is applied on the bearing by a wave washer or a coned disc spring in the rotary electric machine; and thus, an axial backlash is closed to raise rigidity of the bearing and noise due to vibration is prevented.
As the conventional rotary electric machine, for example, there is one as shown in FIG. 10 and FIG. 11. In FIG. 10, reference numeral 41b denotes a rotary electric machine of a fan driving electric motor; and the rotary electric machine has a motor case 42 and a shaft 44 rotatably supported inside the motor case 42 via a pair of bearings 43, 43. The motor case 42 is composed of a cylindrical case body (frame) 45, a front cover 46 which covers a front end opening of the case body 45, and a rear cover 47 which covers a rear end opening of the case body 45. 51 denotes an outer ring of the bearing 43; 52 denotes an inner ring of the bearing 43; and 53 denotes rolling elements provided in plural numbers for each between an outer ring track of the inner circumferential surface of the outer ring 51 and an inner ring track of the outer circumferential surface of the inner ring 52. 54 denotes a corrugated plate spring which is held in sandwiched relation between the side surface of the bracket 49 and the end surface of the outer ring 51 of the bearing 43 to press the outer ring 51 toward the other outer ring 51. 55 denotes a rotor; and 56 denotes a stator. 60b denotes an insulating member mounted between the outer ring 51 of the bearing 43 and the bearing box 61b of each of the brackets 48, 49.
FIG. 11 shows details of a bearing portion. The insulating member 60b is fitted inside the bearing box 61b of the bracket 48; and the bearing 43 is supported via the insulating member 60b and thus electrolytic corrosion is prevented. Furthermore, the preload spring 54 such as a wave washer or a coned disc spring is located between the side surface of the outer ring 51 of the bearing 43 and the side surface of the insulating member 60b. 